The vong imo (especially aesthetically, despite coming first) are glorified space Darkspawn that are supposed to be so great, powerful, and mighty. I am fine with adding new villains or creating more interesting cultures (why I love Old Republic era Mandos) but I am definitely perplexed as it why it was a good idea to introduce a race from another galaxy that slaughters endlessly and then end the series by making peace with that race.

Now it has been quite a while since I read up on Vong history so I may have some things wrong, but here goes...

The Yuuzhan Vong were originally native to the living planet Zonama Sekot. This means that they were also originally native to the galaxy. They may have also at one been point have been part of the Living Force like everything else. Something happened, however, and they were kicked off the planet, separated from the Force and banished from the galaxy.

Peace was made with them due to the re-emergence of Zonama Sekot over Coruscant. That was a huge factor to ending the war. Now mind you the Vong were being defeated by this time but the arrival of Zonama Sekot helped bring the war to a quicker end.

Like I said, it has been a long time since I have read up on Vong history and all this is from pure memory. If I am wrong on any of it I apologize in advance. But hopefully there is enough here that is correct, or close enough, that it clarifies some things for you